So the only way to connect power via the onboard MCP1700 regulator is to the USB port? If that is the case, can I use lower voltage then 5 V to the USB? I cant go via the NCP1117, it has to high dropout.

Or maybe would my best option be to put a TO-92 LDO in the 3.3 VIN holes, like a LE33CZ for example?